Diagnostic value of diffusion-weighted MRI for imaging synovitis in pediatric patients with inflammatory conditions of the knee joint

Background Diffusion-weighted imaging(DWI)of synovitis has been suggested as a possible non-invasive alternative to contrast-enhanced T1w imaging(ce-T1w).We aimed to study DWI for diagnosing synovitis in the knee joint of pediatric patients,to quantify inter-observer agreement on DWI and ce-T1w and to calculate quantitative measures of synovial diffusivity and conspicuity.Methods Forty consecutive patients with known or suspected arthritis of the knee(25 girls,median age 12 years)underwent routine 1.5T MRI with ce-T1w and transverse DWI with b values 50 and 800 s/mm2.Mean apparent diffusion coefficient(ADC)values and signal intensity of inflamed synovium,joint effusion and muscle were measured with regions of interest retrospectively.Post-contrast T1 w images(diagnostic standard)and diffusion-weighted images at b=800 s/mm2 with ADC map were separately rated by three independent and blinded readers with different levels of expertise for the presence and degree of synovitis along with the level of diagnostic confidence.Results Thirty-one(78%)patients showed at least some synovial contrast enhancement,17(43%)children were diagnosed with synovitis on ce-T1w.Ratings by the 1st reader on ce-T1w and on DWI for synovitis showed very good agreement(kappa=0.90).Inter-observer agreement on DWI ranged from moderate to substantial with kappa values between 0.68 and 0.79(all P<0.001).Agreement and diagnostic confidence were generally lower in patients with mild and without synovial enhancement,compared to patients with synovitis.DWI yielded higher signal of inflamed synovium vs.muscle tissue,but lower signal vs.joint effusion,compared to ce-T1 w(all P<0.001).Conclusions Diffusion-weighted imaging is a promising,though reader-dependent alternative to contrast-enhanced imaging in patients with arthritis of the knee,based on our preliminary findings.It holds potential for increasing patient safety and comfort.

CAIPIRINHA-accelerated T1w 3D-FLASH for small-bowel MR imaging in pediatric patients with Crohn's disease:assessment of image quality and diagnostic performance

Background:The“Controlled Aliasing In Parallel Imaging Results In Higher Acceleration”(CAPIRINHA)technique greatly accelerates T1w 3D fast low angle shot(FLASH)scans while maintaining high image quality.We studied image quality and conspicuity of inflammatory lesions on CAIPIRINHA-accelerated imaging for pediatric small-bowel magnetic resonance imaging(MRI).Methods:Forty-four consecutive patients(mean 14±3 years,18 girls)underwent small-bowel MRI(MR enterography,MRE)at 1.5 T including diffusion-weighted imaging(DWI),contrast-enhanced CAIPIRINHA 3D-FLASH and standard 2D-FLASH imaging.Crohn’s disease(CD)was confirmed in 26 patients,18 patients served as control.Independent blinded readings were performed for grading of image quality and conspicuity of CD lesions on CAIPIRINHA FLASH and standard FLASH images in comparison to a reference standard comprising imaging and endoscopic data.Results:CAIPIRINHA FLASH yielded significantly higher image quality with good inter-observer agreement(κ=0.68)and showed better visual delineation in 40%of the assessed bowel lesions,as compared to standard FLASH.There was full agreement for identification of CD patients between CAIPIRINHA and standard FLASH.CAIPIRINHA FLASH detected two small-bowel lesions that were not seen on standard FLASH.DWI revealed additional inflammatory lesions inconspicuous on contrast-enhanced imaging.MRE showed an overall diagnostic accuracy of 93%.Conclusion:We present first evidence that CAIPIRINHA greatly accelerates T1w imaging in paediatric MRE without trade-off in image quality or lesion conspicuity and is thus preferable to standard FLASH imaging.